1. Field of the Invention
The present invention relates to a fingerprint identification system, apparatus, and method for reading a fingerprint from a human finger and comparing the fingerprint against a fingerprint which has been registered in advance, for example, for the purpose of authentication. The present invention also relates to a biometric identification apparatus for reading biometric information relating to a feature of a human body and comparing the biometric information against biometric information which has been registered in advance, for example, for the purpose of authentication.
2. Description of the Related Art
In a system using electronic money, such as electronic commerce on the Internet, user authentication is essential, and fingerprint identification techniques can be used as a means for that purpose.
FIG. 15 is an external view of a conventional fingerprint identification apparatus which is used for such authentication. Referring to FIG. 15, a fingerprint sensor 104 is provided on a surface of a case of a fingerprint identification apparatus 102. A person who is to input his/her fingerprint places his/her finger on a reading unit 108 of the fingerprint sensor 104. Thus, the fingerprint sensor 104 reads the fingerprint, outputting an image signal representing the fingerprint. The fingerprint identification apparatus 102 generates image data of the fingerprint based on the image signal, and analyzes the image data to determine whether the fingerprint which has been read is a particular fingerprint, i.e., whether the person who has input his/her fingerprint is a particular person who has already been registered. For example, a computer (not shown) is notified of the identification result via a cable 110.
Recently, a semiconductor sensor has come to be used as the fingerprint sensor 104, in particular, of the type which detects variation in capacitance due to ridges and valleys of the fingerprint of a finger placed on the fingerprint reading unit 108 (e.g., Japanese Unexamined Patent Application Publication No. 2001-056204).
With regard to methods of fingerprint identification, minutiae method which uses data relating to feature points such as bifurcations and ridge endings of a fingerprint, pattern matching method which compares binarized image data, and a method which performs identification based on the cycle of ridges and valleys of a fingerprint have hitherto been known.
Among them, pattern matching method uses a relatively simple algorithm, and is therefore suitable to implement a fingerprint identification circuit by an LSI (large scale integration circuit), which is advantageous in reducing cost of the apparatus and improving processing speed.
When a fingerprint is identified by pattern matching (e.g., Japanese Unexamined Patent Application Publication No. 58-176781), grayscale image data of the fingerprint is first binarized, and then compared against template image data which has been stored in advance.
Hitherto, in pattern matching method, assuming that features of a fingerprint exists mainly in the central portion thereof, template image data has usually been created and stored by extracting image data representing only the central portion of the fingerprint. At the time of identification, an image representing a larger region of a fingerprint which has been read by a fingerprint sensor at the time of identification, shown in FIG. 16A, is compared against the template image representing a smaller region of a fingerprint, shown in FIG. 16B.
The fingerprint sensor of the type which detects capacitance is relatively expensive. Furthermore, the fingerprint sensor has a large number of cells (elements) for detecting capacitance, and thus is more expensive as the size increases. Accordingly, it is effective to reduce cost of the fingerprint sensor, particularly to use a fingerprint sensor of a smaller size with a smaller number of elements, in order to reduce cost of the fingerprint identification apparatus.
However, if a fingerprint sensor having a smaller number of elements and therefore having a smaller reading region is used, the region of a fingerprint which is read at the time of identification does not necessarily coincide with the region of a fingerprint which has been stored as a template, inhibiting fingerprint identification, and thus causing the inconvenience that a person who is to input his/her fingerprint is required to let his/her finger be read many times.